Tire balancing

ABSTRACT

A method and composition of matter for balancing tire and rim assemblies of vehicles is disclosed wherein the composition of matter has rounded balancing elements of different size to line the interior of a tire casing and to move over the lining to offset points of imbalance.

The following is a continuation of U.S. patent application Ser. No.08/977,335 filed Nov. 24, 1997, now abandoned, which is acontinuation-in-part of U.S. patent application Ser. No. 08/251,507filed May 31, 1994, now U.S. Pat. No. 5,766,501.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to an improvement in a method of balancing tiresusing a free flowing material within a tire casing and in thecomposition of said material.

Most tire and rim assemblies require balancing to prevent vibrationwithin the vehicle while it is in motion. One currently popular, methodof balancing tire and rim assemblies involves rotation of the assemblyon a computerized balancing machine to determine the location and sizeof weights necessary to obtain balanced rotation. Lead weights of thedetermined size are then clamped to the assembly at the indicated pointsto complete the balancing procedure. There are other similar "fixedweight" systems know for tire balancing. Some disadvantages of this typeof system are that tire balancing equipment in expensive, tire balancingrequires a skilled operator and is time consuming, and tires must berebalanced at regular intervals due to effects of varying tread wear.

Continuous self-balancing systems overcome many of the disadvantages ofthe above fixed weight systems. Continuous self balancing systems usethe principle that free flowing materials contained in vessel inrotation will seek a distribution in the balance about the center ofrotation and will tend to offset, by mass damping, any imbalanceinherent in the vessel. The effectiveness of a dynamic balancing systemis dependent in part on the ease with which balancing material can movewithin the vessel to positions, which offset points of imbalance.

In one application of this principle an annular ring is placedcircumferentially about a rim and partially filled with heavy materialsthat will flow under the influence of centrifugal force. One suchbalancer uses mobile weights such as ball bearings, which are free toroll to any point on the ring. The effectiveness of this method islimited by the roundness of the ball bearings, the concentricity of thering to the geometric axis and the inherent rolling resistance of theballs in the ring.

Liquids have been attempted in self-balancing systems to improve themobility of the balancing material. U.S. Pat. No. 2,687,918 to Belldiscloses an annular tube attached to a tire rim partially filled withmercury for continuous balancing of the tire and rim assembly. Severaldisadvantages exist for this method, the principal ones being high costand toxicity of mercury, the difficulty of ensuring concentricity of theannular tube and the need for special rims.

The use of free flowing powdered materials in balancing compensators wastaught in U.S. Pat. No. 4,109,549, in which an annular tube was filledwith other dense materials such as powdered tungsten.

A different means for applying the self balancing principle wasdisclosed in U.S. Pat. No. 5,073,217 to Fogal. A free flowing balancingpowder was placed directly within a pneumatic tire, instead of within aconcentric annular tube. Pulverent polymeric/copolymeric syntheticplastic material in the range of 8-12 screen size and 40-200 screen sizewere disclosed. The patent taught that the powder within the tire woulddistribute within the tire under centrifugal forces to dampen vibration.Placing the balancing media within the tire has two primary advantages.The balancing force is positioned close to the point of imbalance andextraneous annular rings are not required. The disadvantage of Fogal isthat powered products produced from a grinder or pulverizer tend to haveparticles with an irregular shape, which increases resistance orfriction to fluidity. It is unlikely that heavy liquids, such asmercury, could be substituted advantageously in Fogal's application,however, both because of above mentioned safety reasons and because suchliquids may be incompatible with or corrosive to the composition of atire.

It is an object of the present invention to provide a method of tirebalancing using an improved solid particulate material within a tirecasing to obtain better fluidity for more efficient balancing of a tireand rim assembly.

The present invention uses the known principle of balancing through massdamping and the known method of using a solid materials within apneumatic tire to obtain a dynamic balance while the wheel is inrotation. The improvement of this invention lies primarily in thecomposition of the mixture of the balancing material or media. Apreferred size of this balancing media is in the approximate range of10-50 mesh. The mixture can be comprised of a single media or a mixtureof media. The mixture comprises small, dense bead and larger, less densebeads. Beads of a substantially rounded shaped reduce friction andimprove the mobility of the material during balancing.

The small, dense beads may be formed of atomized metallic particles,which form during atomization as tiny balls. Corrosion resistant metalsuch as bronze, brass, zinc, tin, copper, stainless steel, nickel orsilver or alloys of it may be used. Selection may be made afterconsideration of factors such as cost, availability and suitability forforming into small rounded shapes. In preferred embodiments the metalliccomponent is selected from bronze, brass or zinc and atomized to formtiny balls, hereafter called "micro-spheres". The micro-spheres haveround surfaces, which permit them to roll over each other with lessfriction than sharp edged particles. The metallic micro-spheres have thegreatest density (about 5-9 gr/cm3) of the materials in the mixture sothat they are urged to the outside of the other materials duringrotation. The small size of the micro-spheres enables them to filterthrough the other materials during rotation. The interior circumferenceof a tire is usually riddled with small pockets and ridges producedduring the tire molding process. These surface defects cause erraticmovement of the balancing media and reduce its effectiveness. Duringrotation the micro-spheres are forced against the tire casing to fill inimperfections or voids on the tire wall to form a smooth lining whichallows the remaining balancing media to move about the tire casing withless impediment. The excess of the micro-spheres, after voids and ridgesare leveled, act as part of the balancing material and move to offsetpoints of imbalance.

The larger, less dense beads are also rounded and may be formed fromglass ceramics, alumina, corderite, porcelain or titanates and having adensity in the range of 2-5 gr/cm³. These beads function as the primarybalancing material and form the largest portion by weight of themixture. Glass spheres or beads of density 2-3 gr/cm3 are preferred. Theglass beads are larger but less dense than the metallic micro-spheres.Thus the glass beads tend to ride over the metallic micro-spheres tomove easily to points of imbalance to dampen vibrational energy. Theglass beads are more durable than thermoplastic particles of Fogal andless prone to degradation. A preferred size range for these larger, lessdense beads is 10-50 mesh.

The mixture may also include a partitioning agent, such as vermiculite,mica or other monoclinic non-reactive crystalline minerals, to separateand lubricate the mixture to enable all components of the mixture tomaintain free-flowing characteristics. Vermiculite is preferred. Otherpartitioning agents may be used to reduce the friction of the balancingmedia, for example, a lubricant can be applied to the surface of themedia. Such a friction reducing agent could include silicone that issprayed or otherwise applied to the balancing media. Alternatively, thefriction reducing agent may be applied to the interior of the tire suchthat it coats tire rim assembly. Other friction reducing agents, such asTeflon® or the like, may be used in lieu of, or in addition to,silicone.

A suitable desiccant, such as silica gel, A1203, CaC12 or CaS04 may beadded to the mixture to prevent agglomeration in the presence ofmoisture. Silica Gel is preferred as a desiccant to maintain a dryatmosphere in the tire casing. The small particles used in this type ofbalancing system tend to be hydroscopic and may agglomerate in thepresence of moisture. Agglomerated particles will cause a dramaticreduction in balancing efficiency. The silica gel tends to amelioratethis condition.

A preferred mixture of this invention is as follows.

    ______________________________________                                        MATERIAL       SIZE       CONCENTRATION                                       ______________________________________                                        Non-ferrous atomized metal                                                                   80-325 mesh                                                                              10-25%                                                (e.g., bronze or brass)                                                       Glass beads 20-50 mesh 40-80%                                                 (Lead free - soda lime type)                                                  Vermiculite 20-325 mesh 10-30%                                                Silica Gel 20-40 mesh 2-4%                                                  ______________________________________                                    

It has been found that this invention will work effectively with anyconventional multi-wheel vehicle tire and rim assembly. It will beappreciated, however, that the amount of material to balance aparticular assembly will vary in quantity and proportion, according tothe type of assembly and the size of the tire and rim assembly. Correctamounts and proportions may be determined empirically by persons skilledhaving the benefit of this disclosure and the current state of the art.To illustrate in general terms, a steering tire of a truck (11×24.5) mayrequire about 400 grams while a truck driving tire may require 500 gramsof the mixture. Automobile tires may require only 160 grams of themixture but are much more sensitive to vibration than truck tires andtherefore require more vehicle specific and careful measuring.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures which illustrate a preferred embodiment of thisinvention;

FIG. 1 is an illustration of a tire and rim assembly cut away to showthe interior of the tire casing having the balancing material of thisinvention,

FIG. 2 is an illustration of a cross section of a tire and rim assemblyshowing the balancing material of this invention, and

FIG. 3 is a side sectional view of a tire showing the distribution ofthe mixture of this invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In the figures illustrating this invention like numerals indicate likeelements.

In FIG. 1, a tire (1) is shown mounted on a rim (2) which, in turn, ismounted on an axle (3) of a vehicle (4). The interior of the tire casing(5) is ordinarily filled with air. The balancing material (6) of thisinvention lies about the periphery of the tire case (5) while the wheelis in rotation by reason of the centrifugal force exerted on thematerial (6).

As illustrated in FIG. 2, the interior of the tire casing (5) has manyvoids and surface irregularities (7) (which are accenturated in theallustration).

The atomized metal micro-spheres (8) are shown to lie in and about thesurface irregularities (7) of the tire casing (5). The micro-spheres (8)fill the voids and surface irregularities (7) and form a smooth,slippery surface for movement of the remainder of the balancingmaterial. The excess of the micro-spheres acts as a balancing material.Glass beads (9) roll over the micro-spheres (8) and act as the primarybalancing material. Vermiculite (not shown) and silica gel (not shown)are interspersed in the material to act as a lubricant and a desiccant,respectively.

The preferred proportions of the balancing mixture for use in trucktires is as follows:

    ______________________________________                                               atomized metal                                                                         17%                                                             glass beads 70%                                                               vermiculite 10%                                                               silica gel  3%                                                              ______________________________________                                    

For automobile tires, the preferred mixture is:

    ______________________________________                                               micro-spheres                                                                          24%                                                             glass beads 65%                                                               vermiculite  9%                                                               silica gel  2%                                                              ______________________________________                                    

In operation, the balancing mixture may be poured into a new tire casingas it is assembled onto a rim. In tire rim assemblies previouslyconstructed, the sealing bead about the rim may be broken and themixture poured into the tire casing. Alternatively the mixture may bepoured into the valve stem or mixed with the air which pressurized thetire. Once a tire on a vehicle begins to rotate, the balancing material(6) distributes itself within the tire case (5). As the speed ofrotation increases, the metallic micro-spheres (8) tend to filter to theoutside adjacent the tire casing and to fill the voids and surfaceirregularities (7), thereby forming a smooth inner surface. The lighterand larger glass spheres (9) then roll over the micro-spheres to adjustto a position opposite a point of imbalance (10).

As illustrated in FIG. 3, the material (6) distributes within the tirecasing (5) so that a thicker portion of the material (6) lies oppositethe point of imbalance (10), while some of the balancing material (6) isdistributed about the entire inner surface of the tire casing (5). Thedistribution of the balancing material (6) acts as mass damping toovercome the eccentric force which would otherwise be introduced by thepoint of imbalance (10), so that the tire (1) turns smoothly.

We claim:
 1. A method for continuous self balancing of a tire rimassembly during rotation comprising, in combination, the stepsof,providing a tire rim assembly having a hollow tire casing surroundingthe space about the rim defining an interior space and having a point ofimbalance when the interior of the tire is pressurized with air; addinga balancing media comprising solid spherically shaped particulatematerial selected from the group consisting of glass, ceramics, alumina,corderite, porcelain and titanates into the interior space of the tirecasing before or during pressurization with air, the balancing mediahaving a size of about 20-40 mesh; rotating the tire rim assembly todistribute the balancing media within the tire casing; and continuouslyself-balancing the tire rim assembly by rotating the pressurized tirerim assembly and distributing the balance media within the tire casingso that a thicker portion of the balancing media lies opposite the pointof imbalance.
 2. The method according to claim 1 wherein the balancingmedia further comprises a desiccant to maintain a dry atmosphere withinthe tire casing pressurized with air.
 3. The method according to claim 1wherein the balancing media further comprises a partitioning agentreducing friction between the spherical solid particulate material andthe tire casing.
 4. The method according to claim 1 wherein the solidparticulate material has a density of about 2-5 gr/cm³.
 5. The methodaccording to claim 1 wherein the balancing media is added duringpressurization of the tire rim assembly.
 6. The method according toclaim 1 wherein the balancing media is added during the assembly of thetire and rim.
 7. The method according to claim 1, 2, 3, or 4 wherein thesolid particulate material comprises glass beads.
 8. A system formaintaining a rotating tire rim assembly in balance comprising:a tirerim assembly having a hollow casing surrounding a space about the rimand having a point of imbalance when said space is pressurized with air;and a balancing media located in the interior of the tire casing,wherein the balancing media comprises a solid spherically shapedparticulate material selected from the group consisting of glass,ceramics, alumina, corderite, porcelain and titanates, the balancingmedia having a size of about 20-40 mesh so that when the tire rimassembly is rotated the balancing media is distributed within the tirecasing so that a thicker portion of the balancing media lies oppositethe point of imbalance.
 9. The system according to claim 8 wherein thebalancing media further comprises a desiccant to maintain a dryatmosphere within the tire casing pressurized with air.
 10. The systemaccording to claim 8 wherein the balancing media further comprises apartitioning agent reducing friction between the spherical solidparticulate material and the tire casing.
 11. The system according toclaim 8 wherein the solid particulate material has a density of about2-5 gr/cm³.
 12. The system according to claims 8, 9, 10 or 11 whereinthe solid particulate material spherical in shape comprises glass beads.